Clarification of effect of transformed layer and oil film on low friction coefficient of CNx coating in PAO oil lubrication by in-situ observation of friction area with reflectance spectroscopy

Nishimura, Hidenori; Umehara, Noritsugu; Kousaka, Hiroyuki; Murashima, Motoyuki

doi:10.1016/j.triboint.2016.10.029

Cited by 26 publications

(12 citation statements)

References 9 publications

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“…It is well known that carbonaceous structures of DLC coatings strongly affect tribological properties, especially for low friction. 36,40,64 Raman analysis reveals the nature of carbonaceous structures by measuring…”

Section: Surface Analysis Of the Tribolayer On The Dlc-coated Diskmentioning

confidence: 99%

“…[31][32][33] Several studies show that DLC coatings exhibit low friction (<0.05) under some dry conditions. [34][35][36][37] However, it is still difficult to reduce friction in the ambient air. Therefore, some studies used surface treatment or elemental-doping methods to reduce friction.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, the discharge is considered to penetrate the coating. As a result, it is considered that the material removed from the groove transforms into graphitelike structures due to the high discharge energy.It is well known that carbonaceous structures of DLC coatings strongly affect tribological properties, especially for low friction 36,40,64. Raman analysis reveals the nature of carbonaceous structures by measuring…”

mentioning

confidence: 99%

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Development of a new diamond-like carbon surface treatment method with electric discharge for short running-in and friction reduction

Murashima

Maeda

Deng

et al. 2021

Proceedings of the Institution of Mechanical Engineers, Part J:

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The present paper proposes a new treatment method for diamond-like carbon (DLC) coatings using electric discharge. DLC coatings exhibit excellent mechanical and tribological properties due to their unique carbonaceous structure. Several surface treatment methods were presented to achieve short running-in and low friction. However, in-situ surface treatment is needed to extend the life of machines and maintain their performance. Here, we propose an electric discharge treatment with a simple electrical circuit. As a result, the friction coefficient drastically drops from 0.3 to 0.11. Interestingly, the drop starts shortly after the discharge starts. Consequently, the running-in is shortened to about 6-m sliding compared to no discharge condition, which does not show any running-in more than 68-m sliding. Raman analysis reveals that a transfer layer on the ball surface is composed of carbonaceous material and the structure exhibits graphite-like characteristics. However, there is visible damage on the DLC surface. Another friction test shows a very low friction coefficient of 0.04 using a transfer layer-covered ball and a new DLC disk with a smooth surface. In conclusion, the combination of a transfer layer and smooth DLC surface is needed to exhibit excellent tribological performance, indicating the importance of less damage treatment. Next, pulse discharge treatment is demonstrated to achieve less damage to the DLC coating. As a result, the pulse discharge method reduces friction and surface damage. In conclusion, the proposed treatment methods using electric discharge not only show the potential for reducing friction, but also the feasibility of in-situ treatment during machine operation.

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Section: Surface Analysis Of the Tribolayer On The Dlc-coated Diskmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Development of a new diamond-like carbon surface treatment method with electric discharge for short running-in and friction reduction

Murashima

Maeda

Deng

et al. 2021

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…Furthermore, if the light absorption band of the thin film layer is within the measured wavelength range, the Kramers-Kronig relationship can approximate the extinction coefficient spectrum of the wavelength range as a Lorentz type, as shown in Eq. (15).…”

Section: Cnx Coatingmentioning

confidence: 99%

“…Using a wavelength of 589 nm [15] for the analytical values for PAO4 and CN x reflectance index and extinction coefficient, the PAO4 reflectance index was 1.46 and the extinction coefficient was 0.79 × 10 -4 , and for CN x , the reflectance index was 2.06 and the extinction coefficient was 0.85. Because ε PAO4 and ε CNx are known through reflectance spectroscopy, the only unknown from Eq.…”

Section: Cnx Coatingmentioning

confidence: 99%

The Clarification of Friction Mechanism in Oil Lubrication for CNx Coating by In-Situ Observation of Friction Area with Reflectance Spectroscopy

et al. 2021

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To clarify the low friction mechanism of CN x coating in PAO oil lubrication, we measured reflectance spectrum at friction area in-situ by reflectance spectroscopy during friction test against a sapphire hemisphere pin in PAO oil. We observed and estimated the thickness of PAO oil film, the surface roughness of CN x coating, thicknesses, and polarizability of the transformed layer formed on bulk CN x coating during friction test by analyzing reflectance spectrum. We proposed that the decreasing of load ratio of boundary lubrication mode to total load is the one of governing factor to reduce friction on the basis of the increasing of Λ value. Also we proposed the increasing of adsorption of PAO oil to the CN x transformed layer is the second governing factor on the basis of the increasing of polarizability of PAO oil and transformed layer, that leads to the increasing of van der Waals force between transformed layer and PAO oil as low friction mechanism of CN x in PAO oil lubrication.

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Influence of Defects in Graphene-Like Network of Diamond-Like Carbon on Silica Scale Adhesion

et al. 2022

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Silica scale adhesion onto geothermal power plant equipment reduces the power efficiency. In our previous study, diamond-like carbon (DLC) coatings with low sp2 fractions and high hydrogen contents were found to suppress silica adhesion. Therefore, the present study was aimed at clarifying the mechanism of silica adhesion onto the graphene-like network of DLC. In-lens scanning electron microscopic imaging of silica adhered onto defective graphene indicated that the adhesion occurred on defects in the graphene-like network. First-principles calculations revealed that the graphene with hydrogen-terminated defects exhibited reduced adsorption energy between silica and the graphene-like network. Overall, the simulations and experiments helped establish a silica adhesion model in which defects in the graphene-like network of DLC behave as silica adhesion sites. Graphical Abstract

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Clarification of effect of transformed layer and oil film on low friction coefficient of CNx coating in PAO oil lubrication by in-situ observation of friction area with reflectance spectroscopy

Cited by 26 publications

References 9 publications

Development of a new diamond-like carbon surface treatment method with electric discharge for short running-in and friction reduction

Development of a new diamond-like carbon surface treatment method with electric discharge for short running-in and friction reduction

The Clarification of Friction Mechanism in Oil Lubrication for CN<i><sub>x</sub></i> Coating by <i>In-Situ</i> Observation of Friction Area with Reflectance Spectroscopy

Influence of Defects in Graphene-Like Network of Diamond-Like Carbon on Silica Scale Adhesion

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